Sachpazis: Raft Foundation Analysis & Design BS8110:part 1-1997_for MultiStorey Buildings

GEODOMISI Ltd. - Dr. Costas Sachpazis
Civil & Geotechnical Engineering Consulting Company for
Structural Engineering, Soil Mechanics, Rock Mechanics,
Foundation Engineering & Retaining Structures.
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Project: Raft Foundation Analysis & Design, In
accordance with BS8110:part 1-1997_for
multistorey Building.
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Section
Civil & Geotechnical EngineeringCalculations for
Sheet no./rev. 1
Calc.Made by
Dr. C. Sachpazis
Date
27/02/2016
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RAFT FOUNDATION DESIGN IN ACCORDANCE WITH BS8110:PART 1-
1997_FOR MULTISTOREY BUILDING (BS8110 : PART 1 : 1997)
hedge
hboot
bedgebboot
aedge
hslab
hhcoreslab
hhcorethick
AsslabtopAsedgetop
Asslabbtm
Asedgebtm
Asedgelink
Soil and raft definition
Soil definition
Allowable bearing pressure; qallow = 75.0 kN/m
2
Number of types of soil forming sub-soil; Two or more types
Soil density; Firm to loose
Depth of hardcore beneath slab; hhcoreslab = 200 mm; (Dispersal allowed for bearing pressure check)
Depth of hardcore beneath thickenings; hhcorethick = 0 mm; (Dispersal allowed for bearing pressure check)
Density of hardcore; γhcore = 20.0 kN/m
3
Basic assumed diameter of local depression; φdepbasic = 3500mm
Diameter under slab modified for hardcore; φdepslab = φdepbasic - hhcoreslab = 3300 mm
Diameter under thickenings modified for hardcore; φdepthick = φdepbasic - hhcorethick = 3500 mm
Raft slab definition
Max dimension/max dimension between joints; lmax = 12.000 m
Slab thickness; hslab = 250 mm
Concrete strength; fcu = 35 N/mm
2
Poissons ratio of concrete; ν = 0.2
Slab mesh reinforcement strength; fyslab = 500 N/mm
2
Partial safety factor for steel reinforcement; γs = 1.15

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From C&CA document ‘Concrete ground floors’ Table 5
Minimum mesh required in top for shrinkage; A142;
Actual mesh provided in top; A393 (Asslabtop = 393 mm
2
/m)
Mesh provided in bottom; A393 (Asslabbtm = 393 mm
2
/m)
Top mesh bar diameter; φslabtop = 10 mm
Bottom mesh bar diameter; φslabbtm = 10 mm
Cover to top reinforcement; ctop = 20 mm
Cover to bottom reinforcement; cbtm = 40 mm
Average effective depth of top reinforcement; dtslabav = hslab - ctop - φslabtop = 220 mm
Average effective depth of bottom reinforcement; dbslabav = hslab - cbtm - φslabbtm = 200 mm
Overall average effective depth; dslabav = (dtslabav + dbslabav)/2 = 210 mm
Minimum effective depth of top reinforcement; dtslabmin = dtslabav - φslabtop/2 = 215 mm
Minimum effective depth of bottom reinforcement; dbslabmin = dbslabav - φslabbtm/2 = 195 mm
Edge beam definition
Overall depth; hedge = 600 mm
Width; bedge = 550 mm
Depth of boot; hboot = 250 mm
Width of boot; bboot = 250 mm
Angle of chamfer to horizontal; αedge = 60 deg
Strength of main bar reinforcement; fy = 500 N/mm
2
Strength of link reinforcement; fys = 500 N/mm
2
Reinforcement provided in top; 3 H25 bars (Asedgetop = 1473 mm
2
)
Reinforcement provided in bottom; 3 H20 bars (Asedgebtm = 942 mm
2
)
Link reinforcement provided; 2 H12 legs at 250 ctrs (Asv/sv = 0.905 mm)
Bottom cover to links; cbeam = 40 mm
Effective depth of top reinforcement; dedgetop = hedge - ctop - φslabtop - φedgelink - φedgetop/2 = 546 mm
Effective depth of bottom reinforcement; dedgebtm = hedge - cbeam - φedgelink - φedgebtm/2 = 538 mm
Boot main reinforcement; H8 bars at 250 ctrs (Asboot = 201 mm
2
/m)
Effective depth of boot reinforcement; dboot = hboot - cbeam - φboot/2 = 206 mm
Internal beam definition

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Section
Sheet no./rev. 1
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hint
bint
aint
hslab
hhcoreslab
hhcorethick
AsslabtopAsinttop
Asslabbtm
Asintbtm
Asintlink
Overall depth; hint = 550 mm
Width; bint = 500 mm
Angle of chamfer to horizontal; αint = 60 deg
Strength of main bar reinforcement; fy = 500 N/mm
2
Strength of link reinforcement; fys = 500 N/mm
2
Reinforcement provided in top; 3 H25 bars (Asinttop = 1473 mm
2
)
Reinforcement provided in bottom; 3 H25 bars (Asintbtm = 1473 mm
2
)
Link reinforcement provided; 2 H12 legs at 225 ctrs (Asv/sv = 1.005 mm)
Effective depth of top reinforcement; dinttop = hint - ctop - 2 × φslabtop - φinttop/2 = 498 mm
Effective depth of bottom reinforcement; dintbtm = hint - cbeam - φintlink - φintbtm/2 = 486 mm
Internal slab design checks
Basic loading
Slab self weight; wslab = 24 kN/m
3
× hslab = 6.0 kN/m
2
Hardcore; whcoreslab = γhcore × hhcoreslab = 4.0 kN/m
2
Applied loading
Uniformly distributed dead load; wDudl = 2.0 kN/m
2
Uniformly distributed live load; wLudl = 2.5 kN/m
2
Slab load number 1

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Load type; Line load
Dead load; wD1 = 3.0 kN/m
Live load; wL1 = 2.0 kN/m
Ultimate load; wult1 = 1.4 × wD1 + 1.6 × wL1 = 7.4 kN/m
Line load width; b1 = 140 mm
Internal slab bearing pressure check
Total uniform load at formation level; wudl = wslab + whcoreslab + wDudl + wLudl = 14.5 kN/m
2
Bearing pressure beneath load number 1
Net bearing pressure available to resist line load; qnet = qallow - wudl = 60.5 kN/m
2
Net ‘ultimate’ bearing pressure available; qnetult = qnet × wult1/(wD1 + wL1) = 89.5 kN/m
2
Loaded width required at formation; lreq1 = wult1/qnetult = 0.083 m
Effective loaded width at u/side slab; leff1 = max(b1, lreq1 - 2 × hhcoreslab × tan(30)) = 0.140 m
Effective net ult bearing pressure at u/side slab; qnetulteff = qnetult × lreq1/leff1 = 52.9 kN/m
2
Cantilever bending moment; Mcant1 = qnetulteff × [(leff1 - b1)/2]
2
/2 = 0.0 kNm/m
Reinforcement required in bottom
Maximum cantilever moment; Mcantmax = 0.0 kNm/m
K factor; Kslabbp = Mcantmax/(fcu × dbslabmin
2
) = 0.000
Lever arm; zslabbp = dbslabmin × min(0.95, 0.5 + √(0.25 - Kslabbp/0.9)) = 185.3 mm
Area of steel required; Asslabbpreq = Mcantmax/((1.0/γs) × fyslab × zslabbp) = 0 mm
2
/m
PASS - Asslabbpreq <= Asslabbtm - Area of reinforcement provided to distribute the load is adequate
The allowable bearing pressure will not be exceeded
Internal slab bending and shear check
Applied bending moments
Span of slab; lslab = φdepslab + dtslabav = 3520 mm
Ultimate self weight udl; wswult = 1.4 × wslab = 8.4 kN/m
2
Self weight moment at centre; Mcsw = wswult × lslab
2
× (1 + ν) / 64 = 2.0 kNm/m
Self weight moment at edge; Mesw = wswult × lslab
2
/ 32 = 3.3 kNm/m
Self weight shear force at edge; Vsw = wswult × lslab / 4 = 7.4 kN/m
Moments due to applied uniformly distributed loads
Ultimate applied udl; wudlult = 1.4 × wDudl + 1.6 × wLudl = 6.8 kN/m
2
Moment at centre; Mcudl = wudlult × lslab
2
× (1 + ν) / 64 = 1.6 kNm/m
Moment at edge; Meudl = wudlult × lslab
2
/ 32 = 2.6 kNm/m
Shear force at edge; Vudl = wudlult × lslab / 4 = 6.0 kN/m
Moment due to load number 1
Approximate equivalent udl; wudl1 = wult1/(2 × 0.3 × lslab) = 3.5 kN/m
2
Moment at centre; Mc1 = wudl1 × lslab
2
× (1 + ν) / 64 = 0.8 kNm/m
Moment at edge; Me1 = wudl1 × lslab
2
/ 32 = 1.4 kNm/m
Shear force at edge; V1 = wudl1 × lslab / 4 = 3.1 kN/m
Resultant moments and shears
Total moment at edge; MΣe = 7.2 kNm/m

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Total moment at centre; MΣc = 4.3 kNm/m
Total shear force; VΣ = 16.5 kN/m
Reinforcement required in top
K factor; Kslabtop = MΣe/(fcu × dtslabav
2
) = 0.004
Lever arm; zslabtop = dtslabav × min(0.95, 0.5 + √(0.25 - Kslabtop/0.9)) = 209.0 mm
Area of steel required for bending; Asslabtopbend = MΣe/((1.0/γs) × fyslab × zslabtop) = 80 mm
2
/m
Minimum area of steel required; Asslabmin = 0.0013 × hslab = 325 mm
2
/m
Area of steel required; Asslabtopreq = max(Asslabtopbend, Asslabmin) = 325 mm
2
/m
PASS - Asslabtopreq <= Asslabtop - Area of reinforcement provided in top to span local depressions is adequate
K factor; Kslabbtm = MΣc/(fcu × dbslabav
2
) = 0.003
Lever arm; zslabbtm = dbslabav × min(0.95, 0.5 + √(0.25 - Kslabbtm/0.9)) = 190.0 mm
Area of steel required for bending; Asslabbtmbend = MΣc/((1.0/γs) × fyslab × zslabbtm) = 53 mm
2
/m
Area of steel required; Asslabbtmreq = max(Asslabbtmbend, Asslabmin) = 325 mm
2
/m
PASS - Asslabbtmreq <= Asslabbtm - Area of reinforcement provided in bottom to span local depressions is adequate
Shear check
Applied shear stress; v = VΣ/dtslabmin = 0.077 N/mm
2
Tension steel ratio; ρ = 100 × Asslabtop/dtslabmin = 0.183
From BS8110-1:1997 - Table 3.8;
Design concrete shear strength; vc = 0.469 N/mm
2
PASS - v <= vc - Shear capacity of the slab is adequate
Internal slab deflection check
Basic allowable span to depth ratio; Ratiobasic = 26.0
Moment factor; Mfactor = MΣc/dbslabav
2
= 0.109 N/mm
2
Steel service stress; fs = 2/3 × fyslab × Asslabbtmbend/Asslabbtm = 44.615 N/mm
2
Modification factor; MFslab = min(2.0, 0.55 + [(477N/mm
2
- fs)/(120 × (0.9N/mm
2
+ Mfactor))])
MFslab = 2.000
Modified allowable span to depth ratio; Ratioallow = Ratiobasic × MFslab = 52.000
Actual span to depth ratio; Ratioactual = lslab/ dbslabav = 17.600
PASS - Ratioactual <= Ratioallow - Slab span to depth ratio is adequate
Edge beam design checks
Basic loading
Hardcore; whcorethick = γhcore × hhcorethick = 0.0 kN/m
2
Edge beam
Rectangular beam element; wbeam = 24 kN/m
3
× hedge × bedge = 7.9 kN/m
Boot element; wboot = 24 kN/m3
× hboot × bboot = 1.5 kN/m
Chamfer element; wchamfer = 24 kN/m
3
× (hedge - hslab)
2
/(2 × tan(αedge)) = 0.8 kN/m
Slab element; wslabelmt = 24 kN/m
3
× hslab × (hedge - hslab)/tan(αedge) = 1.2 kN/m
Edge beam self weight; wedge = wbeam + wboot + wchamfer + wslabelmt = 11.5 kN/m

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Sheet no./rev. 1
Calc.Made by
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Date
27/02/2016
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Page 6 of 14
Edge load number 1
Load type; Longitudinal line load
Dead load; wDedge1 = 13.2 kN/m
Live load; wLedge1 = 0.0 kN/m
Ultimate load; wultedge1 = 1.4 × wDedge1 + 1.6 × wLedge1 = 18.5 kN/m
Longitudinal line load width; bedge1 = 102 mm
Centroid of load from outside face of raft; xedge1 = 51 mm
Edge load number 2
Dead load; wDedge2 = 16.1 kN/m
Live load; wLedge2 = 5.6 kN/m
Ultimate load; wultedge2 = 1.4 × wDedge2 + 1.6 × wLedge2 = 31.5 kN/m
Longitudinal line load width; bedge2 = 100 mm
Centroid of load from outside face of raft; xedge2 = 230 mm
Edge beam bearing pressure check
Effective bearing width of edge beam; bbearing = bedge + bboot + (hedge - hslab)/tan(αedge) = 1002 mm
Total uniform load at formation level; wudledge = wDudl+wLudl+wedge/bbearing+whcorethick = 16.0 kN/m
2
Centroid of longitudinal and equivalent line loads from outside face of raft
Load x distance for edge load 1; Moment1 = wultedge1 × xedge1 = 0.9 kN
Load x distance for edge load 2; Moment2 = wultedge2 × xedge2 = 7.2 kN
Sum of ultimate longitud’l and equivalent line loads; ΣUDL = 50.0 kN/m
Sum of load x distances; ΣMoment = 8.2 kN
Centroid of loads; xbar = ΣMoment/ΣUDL = 164 mm
Initially assume no moment transferred into slab due to load/reaction eccentricity
Sum of unfactored longitud’l and eff’tive line loads; ΣUDLsls = 34.9 kN/m
Allowable bearing width; ballow = 2 × xbar + 2 × hhcoreslab × tan(30) = 559 mm
Bearing pressure due to line/point loads; qlinepoint = ΣUDLsls/ ballow = 62.5 kN/m
2
Total applied bearing pressure; qedge = qlinepoint + wudledge = 78.4 kN/m
2
qedge > qallow - The slab is required to resist a moment due to eccentricity
Now assume moment due to load/reaction eccentricity is resisted by slab
Bearing width required; breq = ΣUDLsls/(qallow - wudledge) = 591 mm
Effective bearing width at u/s of slab; breqeff = breq - 2 × hhcoreslab × tan(30) = 360 mm
Load/reaction eccentricity; e = breqeff/2 - xbar = 16 mm
Ultimate moment to be resisted by slab; Mecc = ΣUDL × e = 0.8 kNm/m
From slab bending check
Moment due to depression under slab (hogging); MΣe = 7.2 kNm/m
Total moment to be resisted by slab top steel; Mslabtop = Mecc + MΣe = 8.1 kNm/m
K factor; Kslab = Mslabtop/(fcu × dtslabmin
2
) = 0.005
Lever arm; zslab = dtslabmin × min(0.95, 0.5 + √(0.25 - Kslab/0.9)) = 204 mm
Area of steel required; Asslabreq = Mslabtop/((1.0/γs) × 460 N/mm
2
× zslab) = 99 mm
2
/m

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Date
27/02/2016
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Page 7 of 14
PASS - Asslabreq <= Asslabtop - Area of reinforcement provided to transfer moment into slab is adequate
The allowable bearing pressure under the edge beam will not be exceeded
Edge beam bending check
Divider for moments due to udl’s; βudl = 12.0
Span of edge beam; ledge = φdepthick + dedgetop = 4045 mm
Ultimate self weight udl; wedgeult = 1.4 × wedge = 16.1 kN/m
Ultimate slab udl (approx); wedgeslab = max(0 kN/m,1.4×wslab×((φdepthick/2×3/4)-(bedge+(hedge-hslab)/tan(αedge))))
wedgeslab = 4.7 kN/m
Self weight and slab bending moment; Medgesw = (wedgeult + wedgeslab) × ledge
2
/βudl = 28.3 kNm
Self weight shear force; Vedgesw = (wedgeult + wedgeslab) × ledge/2 = 42.0 kN
Ultimate udl (approx); wedgeudl = wudlult × φdepthick/2 × 3/4 = 8.9 kN/m
Bending moment; Medgeudl = wedgeudl × ledge
2
/βudl = 12.2 kNm
Shear force; Vedgeudl = wedgeudl × ledge/2 = 18.1 kN
Moment and shear due to load number 1
Bending moment; Medge1 = wultedge1 × ledge
2
/βudl = 25.2 kNm
Shear force; Vedge1 = wultedge1 × ledge/2 = 37.4 kN
Bending moment; Medge2 = wultedge2 × ledge
2
/βudl = 43.0 kNm
Shear force; Vedge2 = wultedge2 × ledge/2 = 63.7 kN
Total moment (hogging and sagging); MΣedge = 108.7 kNm
Maximum shear force; VΣedge = 161.2 kN
Width of section in compression zone; bedgetop = bedge + bboot = 800 mm
Average web width; bw = bedge + (hedge/tan(αedge))/2 = 723 mm
K factor; Kedgetop = MΣedge/(fcu × bedgetop × dedgetop
2
) = 0.013
Lever arm; zedgetop = dedgetop × min(0.95, 0.5 + √(0.25 - Kedgetop/0.9)) = 518 mm
Area of steel required for bending; Asedgetopbend = MΣedge/((1.0/γs) × fy × zedgetop) = 482 mm
2
Minimum area of steel required; Asedgetopmin = 0.0013 × 1.0 × bw × hedge = 564 mm
2
Area of steel required; Asedgetopreq = max(Asedgetopbend, Asedgetopmin) = 564 mm
2
PASS - Asedgetopreq <= Asedgetop - Area of reinforcement provided in top of edge beams is adequate
Width of section in compression zone; bedgebtm = bedge + (hedge - hslab)/tan(αedge) + 0.1 × ledge = 1157 mm
K factor; Kedgebtm = MΣedge/(fcu × bedgebtm × dedgebtm
2
) = 0.009
Lever arm; zedgebtm = dedgebtm × min(0.95, 0.5 + √(0.25 - Kedgebtm/0.9)) = 511 mm
Area of steel required for bending; Asedgebtmbend = MΣedge/((1.0/γs) × fy × zedgebtm) = 489 mm
2
Minimum area of steel required; Asedgebtmmin = 0.0013 × 1.0 × bw × hedge = 564 mm
2

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Page 8 of 14
Area of steel required; Asedgebtmreq = max(Asedgebtmbend, Asedgebtmmin) = 564 mm
2
PASS - Asedgebtmreq <= Asedgebtm - Area of reinforcement provided in bottom of edge beams is adequate
Edge beam shear check
Applied shear stress; vedge = VΣedge/(bw × dedgetop) = 0.409 N/mm
2
Tension steel ratio; ρedge = 100 × Asedgetop/(bw × dedgetop) = 0.373
From BS8110-1:1997 - Table 3.8
Design concrete shear strength; vcedge = 0.509 N/mm
2
vedge <= vcedge + 0.4N/mm
2
- Therefore minimum links required
Link area to spacing ratio required; Asv_upon_svreqedge = 0.4N/mm
2
× bw/((1.0/γs) × fys) = 0.665 mm
Link area to spacing ratio provided; Asv_upon_svprovedge = Nedgelink×π×φedgelink
2
/(4×svedge) = 0.905 mm
PASS - Asv_upon_svreqedge <= Asv_upon_svprovedge - Shear reinforcement provided in edge beams is adequate
Boot design check
Effective cantilever span; lboot = bboot + dboot/2 = 353 mm
Approximate ultimate bearing pressure; qult = 1.55 × qallow = 116.3 kN/m
2
Cantilever moment; Mboot = qult × lboot
2
/2 = 7.2 kNm/m
Shear force; Vboot = qult × lboot = 41.0 kN/m
K factor; Kboot = Mboot/(fcu × dboot
2
) = 0.005
Lever arm; zboot = dboot × min(0.95, 0.5 + √(0.25 - Kboot/0.9)) = 196 mm
Area of reinforcement required; Asbootreq = Mboot/((1.0/γs) × fyboot × zboot) = 85 mm
2
/m
PASS - Asbootreq <= Asboot - Area of reinforcement provided in boot is adequate for bending
Applied shear stress; vboot = Vboot/dboot = 0.199 N/mm
2
Tension steel ratio; ρboot = 100 × Asboot/dboot = 0.098
From BS8110-1:1997 - Table 3.8
Design concrete shear strength; vcboot = 0.384 N/mm
2
PASS - vboot <= vcboot - Shear capacity of the boot is adequate
Corner design checks
Basic loading
Corner load number 1
Load type; Line load in x direction
Dead load; wDcorner1 = 13.2 kN/m
Live load; wLcorner1 = 0.0 kN/m
Ultimate load; wultcorner1 = 1.4 × wDcorner1 + 1.6 × wLcorner1 = 18.5 kN/m
Centroid of load from outside face of raft; ycorner1 = 51 mm
Load type; Line load in x direction
Centroid of load from outside face of raft; ycorner2 = 230 mm

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Page 9 of 14
Load type; Line load in y direction
Centroid of load from outside face of raft; xcorner3 = 51 mm
Corner bearing pressure check
Total uniform load at formation level; wudlcorner = wDudl+wLudl+wedge/bbearing+whcorethick = 16.0 kN/m
2
Net bearing press avail to resist line/point loads; qnetcorner = qallow - wudlcorner = 59.0 kN/m
2
Total line/point loads
Total unfactored line load in x direction; wΣlinex = 34.9 kN/m
Total ultimate line load in x direction; wΣultlinex =50.0 kN/m
Total unfactored line load in y direction; wΣliney = 41.0 kN/m
Total ultimate line load in y direction; wΣultliney = 57.4 kN/m
Total unfactored point load; wΣpoint = 0.0 kN
Total ultimate point load; wΣultpoint = 0.0 kN
Length of side of sq reqd to resist line/point loads; pcorner =[wΣlinex+wΣliney+√((wΣlinex+wΣliney)
2
+4×qnetcorner×wΣpoint)]/(2×qnetcorner)
pcorner = 1286 mm
Bending moment about x-axis due to load/reaction eccentricity
Moment due to load 1 (x line); Mx1 = max(0 kNm, wultcorner1 × pcorner × (pcorner/2 - ycorner1)) = 14.1 kNm
Moment due to load 2 (x line); Mx2 = max(0 kNm, wultcorner2 × pcorner × (pcorner/2 - ycorner2)) = 16.7 kNm
Total moment about x axis; MΣx = 30.8 kNm
Bending moment about y-axis due to load/reaction eccentricity
Moment due to load 3 (y line); My3 = max(0 kNm, wultcorner3 × pcorner × (pcorner/2 - xcorner3)) = 15.2 kNm
Total moment about y axis; MΣy = 35.1 kNm
Check top reinforcement in edge beams for load/reaction eccentric moment
Max moment due to load/reaction eccentricity; MΣ = max(MΣx, MΣy) = 35.1 kNm

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Section
Sheet no./rev. 1
Calc.Made by
Dr. C. Sachpazis
Date
27/02/2016
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Page 10 of 14
Assume all of this moment is resisted by edge beam
From edge beam design checks away from corners
Moment due to edge beam spanning depression; MΣedge = 108.7 kNm
Total moment to be resisted; MΣcornerbp = MΣ + MΣedge = 143.7 kNm
Width of section in compression zone; bedgetop = bedge + bboot = 800 mm
K factor; Kcornerbp = MΣcornerbp/(fcu × bedgetop × dedgetop
2
) = 0.017
Lever arm; zcornerbp = dedgetop × min(0.95, 0.5 + √(0.25 - Kcornerbp/0.9)) = 518 mm
Total area of top steel required; Ascornerbp = MΣcornerbp /((1.0/γs) × fy × zcornerbp) = 638 mm
2
PASS - Ascornerbp <= Asedgetop - Area of reinforcement provided to resist eccentric moment is adequate
The allowable bearing pressure at the corner will not be exceeded
Corner beam bending check
Cantilever span of edge beam; lcorner = φdepthick/√(2) + dedgetop/2 = 2748 mm
Moment and shear due to self weight
Ultimate self weight udl; wedgeult = 1.4 × wedge = 16.1 kN/m
Average ultimate slab udl (approx); wcornerslab = max(0 kN/m,1.4×wslab×(φdepthick/(√(2)×2)-(bedge+(hedge-hslab)/tan(αedge))))
wcornerslab = 4.1 kN/m
Self weight and slab bending moment; Mcornersw = (wedgeult + wcornerslab) × lcorner
2
/2 = 76.1 kNm
Self weight and slab shear force; Vcornersw = (wedgeult + wcornerslab) × lcorner = 55.4 kN
Moment and shear due to udls
Maximum ultimate udl; wcornerudl = ((1.4×wDudl)+(1.6×wLudl)) × φdepthick/√(2) = 16.8 kN/m
Bending moment; Mcornerudl = wcornerudl × lcorner
2
/6 = 21.2 kNm
Shear force; Vcornerudl = wcornerudl × lcorner/2 = 23.1 kN
Moment and shear due to line loads in x direction
Bending moment; Mcornerlinex = wΣultlinex × lcorner
2
/2 = 188.7 kNm
Shear force; Vcornerlinex = wΣultlinex × lcorner = 137.3 kN
Moment and shear due to line loads in y direction
Bending moment; Mcornerliney = wΣultliney × lcorner
2
/2 = 216.7 kNm
Shear force; Vcornerliney = wΣultliney × lcorner = 157.7 kN
Total moments and shears due to point loads
Bending moment about x axis; Mcornerpointx = 0.0 kNm
Bending moment about y axis; Mcornerpointy = 0.0 kNm
Shear force; Vcornerpoint = 0.0 kN
Total moment about x axis; MΣcornerx = Mcornersw+ Mcornerudl+ Mcornerliney+ Mcornerpointx = 313.9 kNm
Total shear force about x axis; VΣcornerx = Vcornersw+ Vcornerudl+ Vcornerliney + Vcornerpoint = 236.2 kN
Total moment about y axis; MΣcornery = Mcornersw+ Mcornerudl+ Mcornerlinex+ Mcornerpointy = 285.9 kNm
Total shear force about y axis; VΣcornery = Vcornersw+ Vcornerudl+ Vcornerlinex + Vcornerpoint = 215.8 kN
Deflection of both edge beams at corner will be the same therefore design for average of these moments and shears
Design bending moment; MΣcorner = (MΣcornerx + MΣcornery)/2 = 299.9 kNm

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Section
Sheet no./rev. 1
Calc.Made by
Dr. C. Sachpazis
Date
27/02/2016
Chk'd by
Date App'd by Date
Page 11 of 14
Design shear force; VΣcorner = (VΣcornerx + VΣcornery)/2 = 226.0 kN
Reinforcement required in top of edge beam
K factor; Kcorner = MΣcorner/(fcu × bedgetop × dedgetop
2
) = 0.036
Lever arm; zcorner = dedgetop × min(0.95, 0.5 + √(0.25 - Kcorner/0.9)) = 518 mm
Area of steel required for bending; Ascornerbend = MΣcorner/((1.0/γs) × fy × zcorner) = 1331 mm
2
Minimum area of steel required; Ascornermin = Asedgetopmin = 564 mm
2
Area of steel required; Ascorner = max(Ascornerbend, Ascornermin) = 1331 mm
2
PASS - Ascorner <= Asedgetop - Area of reinforcement provided in top of edge beams at corners is adequate
Corner beam shear check
Average web width; bw = bedge + (hedge/tan(αedge))/2 = 723 mm
Applied shear stress; vcorner = VΣcorner/(bw × dedgetop) = 0.573 N/mm
2
Tension steel ratio; ρcorner = 100 × Asedgetop/(bw × dedgetop) = 0.373
From BS8110-1:1997 - Table 3.8
Design concrete shear strength; vccorner = 0.471 N/mm
2
vcorner <= vccorner + 0.4N/mm
2
Link area to spacing ratio required; Asv_upon_svreqcorner = 0.4N/mm
2
× bw/((1.0/γs) × fys) = 0.665 mm
Link area to spacing ratio provided; Asv_upon_svprovedge = Nedgelink×π×φedgelink
2
/(4×svedge) = 0.905 mm
PASS - Asv_upon_svreqcorner <= Asv_upon_svprovedge - Shear reinforcement provided in edge beams at corners is
adequate
Corner beam deflection check
Basic allowable span to depth ratio; Ratiobasiccorner = 7.0
Moment factor; Mfactorcorner = MΣcorner/(bedgetop × dedgetop
2
) = 1.260 N/mm
2
Steel service stress; fscorner = 2/3 × fy × Ascornerbend/Asedgetop = 301.285 N/mm
2
Modification factor; MFcorner=min(2.0,0.55+[(477N/mm
2
-fscorner)/(120×(0.9N/mm
2
+Mfactorcorner))])
MFcorner = 1.228
Modified allowable span to depth ratio; Ratioallowcorner = Ratiobasiccorner × MFcorner = 8.596
Actual span to depth ratio; Ratioactualcorner = lcorner/ dedgetop = 5.037
PASS - Ratioactualcorner <= Ratioallowcorner - Edge beam span to depth ratio is adequate
Internal beam design checks
Basic loading
Hardcore; whcorethick = γhcore × hhcorethick = 0.0 kN/m
2
Internal beam self weight; wint=24 kN/m
3
×[(hint×bint)+(hint-hslab)
2
/tan(αint)+2×hslab×(hint-hslab)/tan(αint)]
wint = 9.9 kN/m
Internal beam load number 1
Dead load; wDint1 = 15.0 kN/m
Live load; wLint1 = 5.3 kN/m
Ultimate load; wultint1 = 1.4 × wDint1 + 1.6 × wLint1 = 29.5 kN/m
Longitudinal line load width; bint1 = 140 mm
Centroid of load from centreline of beam; xint1 = 0 mm

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Mobile: (+30) 6936425722 & (+44) 7585939944,
Job Ref.
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Section
Sheet no./rev. 1
Calc.Made by
Dr. C. Sachpazis
Date
27/02/2016
Chk'd by
Date App'd by Date
Page 12 of 14
Internal beam load number 2
Load type; Full transverse line load;
Dead load; wDint2 = 10.0 kN/m
Live load; wLint2 = 4.0 kN/m
Ultimate load; wultint2 = 1.4 × wDint2 + 1.6 × wLint2 = 20.4 kN/m
Transverse line load width; bint2 = 140 mm
Internal beam bearing pressure check
Total uniform load at formation level; wudlint = wDudl+wLudl+whcorethick+24kN/m
3
×hint = 17.7 kN/m
2
Effective point load due to transverse line/point loads
Effective point load due to load 2 (Line load); Wint2 = wultint2 × [bint + 2×(hint - hslab)/tan(αint)] = 17.3 kN
Total effective point load; Wint = 17.3 kN
Minimum width of effective point load; bintmin = 140 mm
Approximate longitudinal dispersal of effective point load
Approx moment capacity of bottom steel; Mintbtm = (1.0/γs) × fy × 0.9 × dintbtm × Asintbtm = 279.8 kNm
Max allow dispersal based on moment capacity; pintmom = [2×Mintbtm + √(4×Mintbtm
2
+2×Wint×Mintbtm×bintmin)]/Wint
pintmom = 64880 mm
Limiting max dispersal to say 5 x beam depth; pint = min(pintmom, 5 × hint) = 2750 mm
Total dispersal length of effective point load; linteff = 2 × pint + bintmin = 5640 mm
Equivalent and total beam line loads
Equivalent ultimate udl of internal load 2; wintudl2 = Wint2/linteff = 3.1 kN/m
Equivalent unfactored udl of internal load 2; wintudl2sls = wintudl2 × (wDint2 + wLint2)/wultint2 = 2.1 kN/m
Sum of factored longitud’l and eff’tive line loads; ΣUDLint = 32.5 kN/m
Sum of unfactored longitud’l and eff’tive line loads; ΣUDLslsint = 22.4 kN/m
Centroid of loads from centreline of internal beam
Load x distance for internal load 1; Momentint1 = wultint1 × xint1 = 0.0 kN
Sum of load x distances; ΣMomentint = 0.0 kN
Centroid of loads; xbarint = ΣMomentint/ΣUDLint = 0.0 mm
Moment due to eccentricity to be resisted by slab; Meccint = ΣUDLint × abs(xbarint) = 0.0 kNm/m
Assume moment due to eccentricity is resisted equally by top steel of slab on one side and bottom steel of slab on other
From slab bending check
Moment due to depression under slab (hogging); MΣe = 7.2 kNm/m
Total moment to be resisted by slab top steel; Mslabtopint = Meccint/2 + MΣe = 7.2 kNm/m
K factor; Kslabtopint = Mslabtopint/(fcu × dtslabmin
2
) = 0.004
Lever arm; zslabtopint = dtslabmin × min(0.95, 0.5 + √(0.25 - Kslabtopint/0.9)) = 204 mm
Area of steel required; Asslabtopintreq = Mslabtopint/((1.0/γs) × fyslab × zslabtopint) = 82 mm
2
/m
PASS - Asslabtopintreq <= Asslabtop - Area of reinforcement in top of slab is adequate to transfer moment into slab
Mt to be resisted by slab btm stl due to load ecc’ty; Mslabbtmint = Meccint/2 = 0.0 kNm/m
K factor; Kslabbtmint = Mslabbtmint/(fcu × dbslabmin
2
) = 0.000
Lever arm; zslabbtmint = dbslabmin × min(0.95, 0.5 + √(0.25-Kslabbtmint/0.9)) = 185 mm
Area of steel required in bottom; Asslabbtmintreq = Mslabbtmint/((1.0/γs) × fyslab × zslabbtmint) = 0 mm
2
/m

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Mobile: (+30) 6936425722 & (+44) 7585939944,
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Section
Sheet no./rev. 1
Calc.Made by
Dr. C. Sachpazis
Date
27/02/2016
Chk'd by
Date App'd by Date
Page 13 of 14
PASS - Asslabbtmintreq <= Asslabbtm - Area of reinforcement in bottom of slab is adequate to transfer moment into slab
Bearing pressure
Initially check bearing pressure based on beam soffit/chamfer width only
Allowable bearing width; bbearint = bint + 2 × (hint - hslab)/tan(αint) = 846 mm
Bearing pressure due to line/point loads; qlinepointint = ΣUDLslsint/bbearint = 26.5 kN/m
2
Total applied bearing pressure; qint = qlinepointint + wudlint = 44.2 kN/m
2
PASS - qint <= qallow - Allowable bearing pressure is not exceeded
Internal beam bending check
Divider for moments due to udl’s; βudl = 12.0
Divider for moments due to point loads; βpoint = 7.0
Span of internal beam; lint = φdepthick + dinttop = 3998 mm
Ultimate self weight udl; wintult = 1.4 × wint = 13.9 kN/m
Ultimate slab udl (approx); wintslab = max(0 kN/m,1.4×wslab×((φdepthick×3/4)-(bint+2×(hint-hslab)/tan(αint))))
wintslab = 14.9 kN/m
Self weight and slab bending moment; Mintsw = (wintult + wintslab) × lint
2
/βudl = 38.4 kNm
Self weight shear force; Vintsw = (wintult + wintslab) × lint/2 = 57.6 kN
Ultimate udl (approx); wintudl = wudlult × φdepthick × 3/4 = 17.9 kN/m
Bending moment; Mintudl = wintudl × lint
2
/βudl = 23.8 kNm
Shear force; Vintudl = wintudl × lint/2 = 35.7 kN
Bending moment; Mint1 = wultint1 × lint
2
/βudl = 39.3 kNm
Shear force; Vint1 = wultint1 × lint/2 = 58.9 kN
Ultimate point load; Wint2 = wultint2 × φdepthick × 3/4 = 53.6 kN
Bending moment; Mint2 = Wint2 × lint/βpoint = 30.6 kNm
Shear force; Vint2 = Wint2 = 53.6 kN
Total moment (hogging and sagging); MΣint = 132.0 kNm
Maximum shear force; VΣint = 205.8 kN
Width of section in compression zone; binttop = bint = 500 mm
Average web width; bwint = bint + hint/tan(αint) = 818 mm
K factor; Kinttop = MΣint/(fcu × binttop × dinttop
2
) = 0.030
Lever arm; zinttop = dinttop × min(0.95, 0.5 + √(0.25 - Kinttop/0.9)) = 473 mm
Area of steel required for bending; Asinttopbend = MΣint/((1.0/γs) × fy × zinttop) = 642 mm
2
Minimum area of steel; Asinttopmin = 0.0013 × bwint × hint = 585 mm
2
Area of steel required; Asinttopreq = max(Asinttopbend, Asinttopmin) = 642 mm
2

Tel.: (+30) 210 5238127, 210 5711263 - Fax.:+30 210 5711461 -
Mobile: (+30) 6936425722 & (+44) 7585939944,
Job Ref.
www.geodomisi.com
Section
Sheet no./rev. 1
Calc.Made by
Dr. C. Sachpazis
Date
27/02/2016
Chk'd by
Date App'd by Date
Page 14 of 14
PASS - Asinttopreq <= Asinttop - Area of reinforcement provided in top of internal beams is adequate
Width of section in compression zone; bintbtm = bint + 2 × (hint - hslab)/tan(αint) + 0.2 × lint = 1646 mm
K factor; Kintbtm = MΣint/(fcu × bintbtm × dintbtm
2
) = 0.010
Lever arm; zintbtm = dintbtm × min(0.95, 0.5 + √(0.25 - Kintbtm/0.9)) = 461 mm
Area of steel required for bending; Asintbtmbend = MΣint/((1.0/γs) × fy × zintbtm) = 658 mm
2
Minimum area of steel required; Asintbtmmin = 0.0013 × 1.0 × bwint × hint = 585 mm
2
Area of steel required; Asintbtmreq = max(Asintbtmbend, Asintbtmmin) = 658 mm
2
PASS - Asintbtmreq <= Asintbtm - Area of reinforcement provided in bottom of internal beams is adequate
Internal beam shear check
Applied shear stress; vint = VΣint/(bwint × dinttop) = 0.506 N/mm
2
Tension steel ratio; ρint = 100 × Asinttop/(bwint × dinttop) = 0.362
From BS8110-1:1997 - Table 3.8
Design concrete shear strength; vcint = 0.477 N/mm
2
vint <= vcint + 0.4N/mm
2
Link area to spacing ratio required; Asv_upon_svreqint = 0.4N/mm
2
× bwint/((1.0/γs) × fys) = 0.752 mm
Link area to spacing ratio provided; Asv_upon_svprovint = Nintlink×π×φintlink
2
/(4×svint) = 1.005 mm
PASS - Asv_upon_svreqint <= Asv_upon_svprovint - Shear reinforcement provided in internal beams is adequate
Tel.: (+30) 210 5238127, 210 5711263 - Fax.:+30 210 5711461 -
Mobile: (+30) 6936425722 & (+44) 7585939944,

Sachpazis: Raft Foundation Analysis & Design BS8110:part 1-1997_for MultiStorey Buildings

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Sachpazis: Raft Foundation Analysis & Design BS8110:part 1-1997_for MultiStorey Buildings